Barely 24 hours after President Obama signed his landmark health law, Gov. Martin O’Malley promised that Maryland would “lead the nation” in putting it in place.

In the three years since, Maryland has been at the forefront of implementing the Affordable Care Act. It established six policy work groups. It trained more than 5,000 people to help consumers enroll in new health-coverage options. When its online insurance exchange passed a critical test in the summer — one of the first in the country to do so — a top official gave an emotional speech thanking workers. If any state was going to be ready for Oct. 1, when millions of uninsured Americans would be able to start buying coverage under the health law, it would be Maryland.

But when Tuesday arrived, Maryland’s Web site stumbled badly. People couldn’t log on, forcing state officials to delay the opening of the exchange for four hours. Even after it opened, many frustrated users were unable to create accounts, the first step in buying coverage. All told, fewer than 100 people have managed to enroll.

Four days after the launch of insurance exchanges — a centerpiece of Obama’s signature health-care law — the online market­places in Maryland, several other states and the federal government continue to have problems. Supporters and critics of the law, also known as Obamacare, are maneuvering to use the technical difficulties to their own advantage.

Defenders say the glitches are caused by higher-than-expected traffic, an indication of the tremendous demand for coverage among the uninsured. They say there is plenty of time to fix the sites; the insurance coverage doesn’t start until Jan. 1. Skeptics say the exchanges might have serious underlying flaws that are not related to traffic volume or easily resolved.

Late Friday, officials at the Department of Health and Human Services said they planned to take down their site, HealthCare.gov, to make fixes during off-peak hours over the weekend. During these maintenance periods, they said, people will still be able to get information through a federal call center. The officials said 8.6 million people had looked at the HealthCare.gov site from Tuesday morning through midnight Thursday. They declined to say how many people have enrolled.

House Speaker John A. Boehner (R-Ohio) called the decision to take the exchange offline for the weekend proof that its launch had been “an unmitigated disaster.”

“What the administration wanted to dismiss as simple glitches have turned out to be a system-wide failure,” he said in a statement. “This announcement is more proof we need to delay the law and provide basic fairness, just as Republicans have called for.”

A few state exchanges are performing well. Connecticut officials threw themselves a party after a successful second day. Kentucky officials had a yellow sheet cake with “100,000” in white icing to mark the number of people who had completed the pre-screening process Wednesday.

In Maryland, some of the problems appear tied to requiring users to set up personal accounts before allowing them to compare health plans and shop for coverage. That feature is creating enormous bottlenecks and blocking users from going any further, officials said.

“Maryland does seem to have more problems than some of the others,” said Robert Moss, an information-technology consultant who has helped states and insurance companies prepare for the launch. “Of course, the federal government site is obviously still having problems, and that’s affecting more states than anybody else.”

The real test for state and federal officials will come a month from now, experts say. “By Nov. 1, they should know for sure whether it’s just a few hiccups. If they’re still having problems, then that’s a bigger problem than just a few bugs in the system,” Moss said.

Maryland officials, using Twitter and Facebook, apologized to those who are still unable to sign on. “Bear with us as our tech team works to resolve the bandwidth issues,” the exchange said in a tweet early Friday.

Joshua Sharfstein, Maryland’s health secretary and chairman of the board overseeing the state exchange, said technicians have been working around the clock to troubleshoot issues as they arise.

In a statement late Friday, a spokeswoman for the Maryland exchange said that officials knew there would be “hiccups” before the launch but that “we remain excited by the overwhelming response we’ve received to Maryland Health Connection in just the first days after its launch.”

She added that technicians have started to resolve the problem involving the accounts and that, as a result, “thousands more user accounts” were created Friday.

Technicians have “identified other areas of the site where functionality could be improved as well,” she added, and the IT team plans to upgrade the system’s software in the next few days. Big chunks of the site will be taken offline every night this month to try to fix the problems.

Peter Beilenson, chief executive of Evergreen Health, one of the insurers selling plans on the Maryland exchange, said information about some of his co-op’s plans is not being properly displayed. And information for out-of-pocket costs on some competitors’ plans is inaccurate, he said.

For Maryland, the problems are embarrassing. As recently as last month, O’Malley, a 2016 Democratic presidential hopeful, was touting his state’s performance in a joint appearance with Texas Gov. Rick Perry (R) on CNN’s “Crossfire.” Attacking Perry for refusing to implement parts of the health-care law, O’Malley said, “I know Texas seceded from the National Governors Association, but if you came, you might be able to learn from the other governors that are actually implementing [the health law], doing it well, and actually doing a better job of supporting an innovation economy and their workers’ well-being.”

O’Malley and his wife have been on a long-planned vacation out of state this week. But the governor has been checking in regularly. One aide said that O’Malley was “very emphatic” in conversations Thursday that he wants the glitches fixed, regardless of what it takes.

“If states like Kentucky are operating well, one would hope that Maryland would join the ranks in the future,” said one industry executive who did not want to be identified for fear of jeopardizing business with the state. “Considering how much effort has been made and resources poured into ensuring a smooth enrollment on the exchange, the first week has been a significant disappointment.”

Kentucky announced Friday that 4,739 individuals or families had enrolled in new health-care coverage. Connecticut has enrolled 1,000 individuals or families. Both Kentucky and Connecticut allow users to browse for plans before requiring them to create an account to purchase insurance.

Kevin Counihan, chief executive of Access Health CT, Connecticut’s exchange, said the goal was to make it as easy for people as possible. In road-testing design features with groups of consumers in recent months, he said, the staff learned that people did not want to have to register first. “It created more fragility and complexity. . . . It’s like buying a car with too many features.”

Amy Goldstein, John Wagner, Sandhya Somashekhar and Alice Crites contributed to this report.

Lena H. Sun is a national reporter for The Washington Post, focusing on health.

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